Orca snot leads to a whale of a science-fair project
PITTSBURGH, Pa. — Killer whales have a distinctive black-and-white, almost tuxedoed appearance. But some groups of these orcas hang out in different areas. Their overall coloration can vary, too. Some groups of these whales even choose to dine on totally different prey. Such divergent traits have led some scientists to propose there might be more than one orca species. But a teen researcher’s new analysis now challenges that.
Orca (Orcinus orca) is the world’s largest dolphin. Its family groups, known as pods, keep pretty much to themselves, notes 18-year-old Luke Harris. He’s a 12th-grader at West Islip High School on New York’s Long Island. A pod’s relative isolation might, over time, lead different populations of the whales to evolve into separate species. Other factors also have suggested there might be at least two orca species. For instance, orcas in some groups eat only fish, such as salmon. A second type will also prey on seals and dolphins. The backs of individuals in some groups are a dark gray, not true black. Finally, some groups of orcas have white patches that are notably larger, on average, than are those on others.
Luke decided to use DNA to settle the question of how many species of orca exist.
Previously, researchers studying other whales, including humpbacks, had shown that it’s possible to get DNA from their “blow.” That’s the spray of mist exhaled through the blowhole as these marine mammals surface to breathe. There’s mucus in that mist, notes Luke. And where there’s mucus, there’s DNA.
Luke enlisted people at SeaWorld to help collect mucus samples from 22 of the orcas at their parks in Florida, Texas and California. Those orcas had come from different pods. He thought the DNA from these individuals might help him learn whether they also represented more than one species.
For his analysis, Luke looked at a gene. This short stretch of DNA is called MT-CO1. The “MT” means that this gene comes from a cell’s mitochondria (My-toh-KON-dree-uh). Those mitochondria, which produce energy in a cell, are passed down to offspring only by females. The “CO1” part of the gene’s name stands for the protein it produces. This protein — an enzyme known as cytochrome (SY-toh-krohm) c oxidase I — speeds up a biochemical reaction that produces water.
Luke chose to analyze this bit of DNA because scientists had shown that its makeup can differ somewhat from one species to another.
The teen's study was the first to extract DNA from the mucus of orcas. The MT-CO1 gene was the same in every whale that he studied. Based on these data, it would seem that all orca pods represent the same species. However, he adds, looking at other orca genes might turn up genetic differences between pods.
Now the teen plans to turn his attention to finding out the best height at which to collect mucus from an orca’s blow. The folks at SeaWorld had collected it on petri dishes held about 30 centimeters (1 foot) above the blowholes. That’s quite close to a whale. But the SeaWorld team could do it, Luke notes, because its orcas had been trained to briefly ascend, upon command, onto a pool deck. At sea, using a drone might be a safer and more reliable way for researchers to sample that spray from whales.
In the past, scientists have used small darts to collect tissue from orcas. But that has its drawbacks. Darts leave a small wound, for instance, that can get infected. Being hit with a dart is painful, too. For example, an orca that’s been darted learns to avoid boats and stays underwater longer than normal when boats are near, Luke points out. Such activity changes would hinder the ability of researchers to study how orcas behave in the wild. Collecting blow via drone, Luke says, should be a kinder, gentler way to study these marine mammals.
The teen shared his results here, last week, at the Intel International Science and Engineering Fair (ISEF). Society for Science & the Public created the competition and has been running it since 1950. (The Society also runs Science News for Students and this blog.) Sponsored by Intel, this year’s competition saw almost 1,800 students from 81 nations, regions and territories vie for roughly $5 million is prizes and scholarships. Nearly one-third of all finalists took home some sort of award.
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
biochemical (adj.) Referring to something made and used within living things.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells.
DNA (short for deoxyribonucleic acid) A long, double-stranded and spiral-shaped molecule inside most living cells that carries genetic instructions. It is built on a backbone of phosphorus, oxygen, and carbon atoms. In all living things, from plants and animals to microbes, these instructions tell cells which molecules to make.
dolphins A highly intelligent group of marine mammals that belong to the toothed-whale family. Members of this group include orcas (killer whales), pilot whales and bottlenose dolphins.
drone A remote-controlled, pilotless aircraft or missile.
egg The unfertilized reproductive cell made by females.
engineering The field of research that uses math and science to solve practical problems.
evolve (adj. evolving) To change gradually over generations, or a long period of time. In living organisms, such an evolution usually involves random changes to genes that will then be passed along to an individual’s offspring. These can lead to new traits, such as altered coloration, new susceptibility to disease or protection from it, or different shaped features (such as legs, antennae, toes or internal organs).
extract (v.) To separate one chemical (or component of something) from a complex mix.
gene (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.
high school A designation for grades nine through 12 in the U.S. system of compulsory public education. High-school graduates may apply to colleges for further, advanced education.
humpback A species of baleen whale (Megaptera novaeangliae), perhaps best known for its novel “songs” that travel great distances underwater. Huge animals, they can grow up to more than 15 meters (or around 50 feet) long and weigh more than 35 metric tons.
Intel International Science and Engineering Fair (Intel ISEF) Initially launched in 1950, this competition is one of three created (and still run) by the Society for Science & the Public. Each year now, approximately 1,800 high school students from more than 80 countries, regions, and territories are awarded the opportunity to showcase their independent research at Intel ISEF and compete for an average of almost $5 million in prizes.
marine mammal Any of many types of mammals that spend most of its life in the ocean environment. These include whales, walruses and sea lions, seals and sea otters, manatees and dugongs — even polar bears.
mitochondria (sing. mitochondrion) Structures in all cells (except bacteria and archaea) that break down nutrients, converting them into a form of energy known as ATP.
mucus A slimy substance produced in the lungs, nose, digestive system and other parts of the body to protect against infection. Mucus is made mainly of water but also includes salt and proteins such as mucins. Some animals use mucus for other purposes, such as to move across the ground or to defend themselves against predators.
orca The largest species of dolphin. The name of this black-and-white marine mammal, Orcinus orca, means killer whale.
pod (in zoology) The name given to a group of toothed whales that travel together, most of them throughout their life, as a group.
population (in biology) A group of individuals from the same species that lives in the same area.
prey (n.) Animal species eaten by others. (v.) To attack and eat another species.
protein A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.
salmon A popular game fish that tends to live most of its life in the ocean, then enters coastal rivers (and freshwater) to breed and lay eggs.
sea An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
Society for Science and the Public A nonprofit organization created in 1921 and based in Washington, D.C. Since its founding, the Society has been promoting not only public engagement in scientific research but also the public understanding of science. It created and continues to run three renowned science competitions: the Regeneron Science Talent Search (begun in 1942), the Intel International Science and Engineering Fair (initially launched in 1950) and Broadcom MASTERS (created in 2010). The Society also publishes award-winning journalism: in Science News (launched in 1922) and Science News for Students (created in 2003). Those magazines also host a series of blogs (including Eureka! Lab).
species A group of similar organisms capable of producing offspring that can survive and reproduce.
sperm The reproductive cell produced by a male animal (or, in plants, produced by male organs). When one joins with an egg, the sperm cell initiates fertilization. This is the first step in creating a new organism.
tissue Made of cells, it is any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.
trait A characteristic feature of something. (in genetics) A quality or characteristic that can be inherited.